1. Field of the Invention
The invention relates to a tractor feed for paper webs with margin perforations for use in printers of data processing systems; more particularly, it relates to a tractor feed having endless band supported feed pins adapted to be manipulated to allow introduction and loading of a paper web and to engage and feed paper webs toward, around and away from a printing platen under the control of movable band guide rails.
2. Description of Related Art
In known tractor feed devices, the paper web is often guided to a platen by means of one pin feed band section and transported away from it by means of the other section, as in e.g. DE-A1 No. 30 46 592 or DE-AS No. 22 33 095. This means that the paper web passes through the tractor pair on top and bottom. This causes particular difficulties when introducing a new paper web. It is for this reason that in relatively flat printer housings the tractors are pivotably mounted to provide access to the underside of the tractor feed. This increases the cost of a printer considerably. To be able to insert the paper into the pins of the band, pivotable guide strips and associated springs are necessary to see to it that they remain in their open position. This makes the known tractor feeds hard to assemble and to handle.